Why are this characther's hands not mirrored while I model it?
1st turn off clipping in your mirror modifier.

In object mode be sure to ensure that rotation and scale are applied Ctrl + A.

Next turn off increment snapping Shift + Tab.

Next set your cursor to the origin of the body.
With the body selected as it is here: Shift + S, Then Cursor to selected.

Next Apply your 3D cursor to the origin: use the . key on the qwerty not the Numpad.

Then Re-Apply the modifier settings.

From the screen-shot above you have a lot going on, so these steps may not be the right answer, but they are definitely worth a shot.

If this still does not work for you, please attach the blend file, so the community can take a look and see were the problem resides.

Hope this helps,

RRiggs